PrincipalInvestigator:Garland,WA ABSTRACT/SUMMARY kRAS is a GTPase which is the main mediator (on/off) of downstream signaling from the EGF receptor (EGF?R)onthesurfaceofcells.kRAScontrolsmajorsignalingsystemssuchastheRAF/MEK1/2/ERK1/2 cell proliferation pathway and the PI3K/AKT/mTOR cell survival pathway. Somatic kRAS mutations, termedoncogenickRAS,arecommoninmanycancers:90%incidenceinpancreatic,45%incolorectal, and 35% in lung cancer. Mutated kRAS allows the EGF?R system to bypass its natural controls and operatenearlycontinuouslyinapro?growthmode.Wild?typekRASisself?inactivating,whileoncogenic kRASisnot.Consistentwiththismechanism,thepresenceofG12VmutatedkRASblockstheefficacyof monoclonal antibody drugs against EGF?R, such as panitumumab (Vectibix) and cetuximab (Erbitux), whichareusedtotreatcolorectalcancer,headandneck,andothercancers. Tosk?s Phase I SBIR research used a proprietary, genetically modified Drosophila melanogaster strain that expresses G12V kRAS in its wings to identify two chemical scaffolds (?hits?) that suppress kRAS? related activity. In addition to phenotype reversal of anti?G12V activity in the mutant fly, the hits were testedinrelevantcellculture,proteinkinase,computationalactivesitedocking,RAF,andSOSpulldown assays.AssessmentofERKactivity,xenograftmodelstudies,andshort?termsafetyandPKstudieswere also performed. Information about the presence, location, and activity of the mutant kRAS gene was also obtained. The repeatability and reproducibility of the G12V fly screens were evaluated and confirmed.Althoughnotconclusive,MOAstudies,includingknockoutstudiesintheG12V?expressingfly, strongly suggest that the hits inhibit kRAS activity in the RAS/RAF/MEK/ERK pathway. Computational docking studies further suggest a direct interaction of the hits with kRAS, possibly leading to interferencewiththekRAS?RAFprotein?proteininteraction. The primary goals of this Phase II SBIR application are to: (1) perform additional screening using an improved version of the Phase I fly assay to discover new kRAS inhibitors, (2) optimize and further characterizethetwoinhibitorsdiscoveredintheSBIRPhaseIandanynewlydiscoveredinhibitorsfrom PhaseII,and(3)usemechanism,efficacy,safety,andpharmacokineticstudiestoselectacandidateand oneback?upreadyforIND?enablingtestsneededtofileanINDforaninhibitorofmutantkRAS.